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Population forecasting of small areas or ethnic groups

Population forecasting of small areas or ethnic groups. Stockholm, 21 st November 2008 Ludi Simpson University of Manchester. www.ccsr.ac.uk/popgroup. Population forecasting: 2 practical dilemmas. Theory without software Cohort component framework

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Population forecasting of small areas or ethnic groups

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  1. Population forecasting of small areas or ethnic groups Stockholm, 21st November 2008 Ludi Simpson University of Manchester www.ccsr.ac.uk/popgroup

  2. Population forecasting: 2 practical dilemmas • Theory without software • Cohort component framework • Multi-regional, probabilistic, socially disaggregated • Academic research • Project-specific • Priority problems without stable data • Sub-national and non-standard areas • Ethnic or national groups • Non-cohort, non-component methods un-informative

  3. Version 1 (1999) – version 3 (2005) • Local/Regional government concerns • Replicate and develop national agency work • Population, housing, and labour force • Impact of local development policies • Ethnically diverse populations • Large populations and systems of small populations • Standard national methods • applied to 1 or more ‘groups’, named by the user

  4. POPGROUP designPrinciples and practice • Excel input files • Excel output files • Macros do work of structuring files, validating data, projections and most interrogation • Easy start, then develop • the future is not what it used to be • Integrate estimates and forecasts

  5. Future popul-ation Base popul-ation Natural change Migration Each component of population change is one input file Pt+1 = Pt + B – D + IUK – OUK +IOV – OOV Seven input files, plus: Constraints : population, housing and employment Special populations (students, armed forces) Dwellings (vacancy, second homes, sharing households) Jobs (commuting, unemployment)

  6. Each input file represents a collection of assumptions for one component

  7. Mathematical approach to combine the varied availability of demographic rates, past counts, and targets

  8. Projecting small populations (areas or ethnic groups) • Few data for non-standard areas • Time series are unstable • Recent past may not indicate an underlying level of fertility, mortality, migration • Alternatives provide neither age nor components • Mathematical extrapolation • Shift share • Housing units

  9. Example 1: replicating District population and household projections. Detailed data available

  10. Household outputs

  11. Household outputs

  12. Example 2: Wards of Bradford.Births, deaths and population available for recent years • Each area’s counts of births indicate its past level of fertility. • Trends that are expected to affect all areas are entered on the ‘All-groups’ sheet • Expressed as a differential to a standard schedule, the area level is continued to the future • Local trends may be identified and used in assumptions for the future

  13. The impact of fertility file options on the Total Fertility Rate Total Fertility Rate Training phase 2. Age-trend on All-areas sheet, from GAD projections Forecasts 3. Each area’s differential, maintained in future 4. Unusual trends may be continued in future 1. Each area’s counts of births

  14. The impact of migration file and constraint options on migration

  15. A cohort component projection allows understanding of population dynamics from incomplete information • Birmingham city: eight ethnic groups • Estimate components of change for each group • Estimate population change due to each component • Present the decomposition of expected population change

  16. Example 3: The impact of housing plans on population • Population and housing change, a two-way relationship • Regional planners are interested • Large areas: how much land should be released for house-building? • Small areas: what is the impact on services of planned house-building? • Greater numbers of houses built may result in… • More in-migration • Less out-migration • Lower household size • Higher proportion of vacancies, or of holiday-homes

  17. POPGROUP alters migration to meet housing constraints(running HOUSEGROUP in the background) What’s the impact on population of planned housing developments? What’s the change in number of households and dwellings each year?

  18. National Parks: ageing populations Decomposition of household change 2001-2016

  19. Peak District National Park: new housing will not create a workforce (unless the migration age structure changes) Population change – Dwelling led projections (2001-25)

  20. Milton Keynes spill-over to Aylesbury Vale (2 wards selected) KEY Green: migration as estimated for 2001-2006. (‘Trend-based’) Red: Zero new dwellings. Black: alternative planned house-building

  21. Discussion • www.ccsr.ac.uk/popgroup • Good forecasts incorporate good estimates • Detailed small area forecasts are possible with few data, if they are relevant data

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